Natural Numbers and Number Lines
Natural numbers are used for counting, ordering and describing quantities. A number line makes addition, subtraction, multiplication and division easier to visualise.
Definitions and notation
Natural numbers are the whole numbers beginning at 0: N = {0, 1, 2, 3, …}. Decimal numbers and negative numbers are not natural numbers. A number line marks equally spaced values and continues indefinitely in the direction of its arrow.
Operations on a number line
- For addition, start at the first number and move right by the second number of units.
- For subtraction, start at the first number and move left by the second number of units.
- Multiplication is repeated addition; division is sharing into equal groups.
Worked examples
- To calculate 4 + 5, start at 4 and move five units right: the answer is 9.
- To calculate 12 − 7, start at 12 and move seven units left: the answer is 5.
- 16 × 4 = 16 + 16 + 16 + 16 = 64, while 20 ÷ 5 = 4 because five equal groups make 20.
Practice
- Place 3, 8 and 13 on a number line.
- Use a number line to find 6 + 7 and 15 − 9.
- Evaluate 14 × 6 and 72 ÷ 8.
